Honda TRX500FGA Owner's Manual page 64

Longitudes, also called meridians, are vertical circles extended from the
North Pole to the South Pole. The zero degree longitude, which passes
through Greenwich, England, divides the Earth into the Eastern and
Western hemispheres. The 180 degree longitude, half way around the
planet, is the international date line.
LONGITUDE
0° longitude
(Greenwich, England)
Western
Hemisphere
Each longitude 69 miles wide
Each time zone equals 15° longitude
Introduction
North Pole
180° longitude
(international date line)
South Pole
GPScape System
Eastern
Hemisphere
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